As will be appreciated by those skilled in the art, a drill wrench is used with apparatus for drilling holes in a mine ceiling and is also commonly used for driving the ceiling bolts into place. In the usual situation a long drill bit and the shaft, usually a piece of drill steel between 2 and 4 feet long, is used to drill a hole into the ceiling of a mine. After drilling the hole, a ceiling bolt is provided for anchoring and helping to support the ceiling so that it does not collapse. In the drilling process, a drill bit is typically fitted into a first end of the hexagon shaped drill steel, which acts as a shaft, and the other end of the drill steel attaches with a sliding fit into a drill wrench. The back end of the drill wrench typically has welded thereto a selected length of hexagon shaped drill steel or a round steel with a hexagon shaped bottom shaft, which in turn fits into a rotating drill head for providing power to the drill bit. The hole is drilled in the mine ceiling, the drill bit and steel attached to the drill bit is removed and a ceiling bolt (commonly with a square head) is inserted into the hole. Many techniques are used for securing the ceiling bolt into the hole, although perhaps the preferable means in modern techniques is to include a quantity of epoxy material at the end of the ceiling bolt which is activated and dries in place when the ceiling bolt itself is driven in place and related to epoxy manufacturer's specifications.
In a typical operation using the techniques available today, it is not uncommon for the length of drill steel which is welded to the back side of the drill wrench to break at the weld point of the drill wrench. Unfortunately, such a break usually results in a significant loss of time and requires immediate repairs. If another drill wrench which has the desired size of drill steel attached is not available, then the broken piece must be sawed away with a hack saw or other metal cutting device and a new piece of drill steel welded thereto. Obviously in the mining environment the use of open flame or sparks from welding are dangerous, and must be done only after proper checking for methane gases and adequate ventilation. Consequently, such repairs often must take place outside of the mine shaft itself.
A search of the applicable classes and references was made with respect to the present invention. Consequently several patents related somewhat to the present idea were found, but none of these patents included the details and features of the present invention. For example, U.S. Pat. No. 2,735,704 issued to B. E. R. Lofqvist on Feb. 21, 1956 discloses a coupling device for joining two hexagon shaped pieces of drill steel of the type used for rock drilling. According to the U.S. Pat. No. 2,735,704 the two pieces of steel are joined by a friction fitting sleeve which fits on the outside of the two matching or mating pairs of drill steel. A pair of dimples are included at the mating ends of the two pieces of steel. These dimples cooperate with a spring loaded key member which itself cooperates with the outside sleeve for holding the two matching pairs of drill steel together.
U.S. Pat. No. 3,519,091 issued to D. L. Leibee, et al. on July 7, 1970 on the other hand discloses the use of a hexagon shaped end on a drive head which includes a split ring such that the hexagon shaped insert will fit tightly and firmly within the interior wall of a hexagon shaped drill steel. The patent also shows how additional lengths of drill steel may be added to increase the length by the use of a double ended mating piece which extends into the interior of two separate pieces of hexagon drill steel.
U.S. Pat. No. 4,009,760 issued to L. B. Hansen, et al. on Mar. 1, 1977 discloses the use of specific types of drilling extensions which come in selected lengths such that the overall length of the drill bit may be extended. However, it is clearly seen that this type device is not compatible with the commonly used hexagon shaped drill steel, driving heads and drill bits.
Similarly, the U.S. Pat. No. 4,226,290 issued to L. H. McSweeney on Oct. 7, 1980 discloses the use of both square shaped and hexagon shaped drives. This patent also provides a good discussion of the actual drilling machinery used for drilling ceiling holes. However, clearly this invention does not disclose the type drilling wrench described in the following discussion.
Therefore, it is an object of the present invention to provide a drill wrench which may be used with various selected lengths of drill steel, and which allows for immediate repair without open flame or spark in the event the drill steel breaks.
It is another object of the present invention to provide an inexpensive drill wrench which can readily be attached to existing machinery and used with existing drill steel.
It is a further object of this invention to provide a new and improved drill wrench which allows for ready exchange of the length of drill steel driving the wrench and bit.
And it is another object of this invention to provide a new and improved drill wrench which is completely compatible with existing drill bits, drive heads and hexagon shaped drill steel.